1. Field of the Invention
The present disclosure relates to injection systems, and more particularly to fuel injection such as used in gas turbine engines.
2. Description of Related Art
A variety of devices and methods are known in the art for fuel injection. Of such devices, many are directed to staged fuel injection, such as in gas turbine engines. In traditional configurations, two or three fuel stages are provided, such as to concentric respective spray orifices. For example, at a low power setting only a pilot stage is needed, whereas at higher power levels, a second or even third fuel stage radially outboard of the pilot stage can be used in addition to the pilot stage to increase the flow rate of the fuel issued. This kind of staging typically involves use of a check or scheduling valve in each injector for activating/deactivating the various fuel stages based on inlet pressure at a manifold that supplies fuel to the injectors. Empty fuel manifolds in an active engine are not desirable due to the unknown response times required to fill the manifold on demand.
Such conventional methods and systems have generally been considered satisfactory for their intended purpose. However, there is still a need in the art for improved staged fuel injection. The present disclosure provides a solution for this need.